This R34 study will advance the science of mental health services for adolescent externalizing problems (AEPs) by developing therapist training procedures to increase fidelity to evidence-based interventions (EBIs) in usual care. Two widely endorsed approaches are consistently effective for treating AEPs: family therapy and CBT. Importantly, stronger fidelity to core EBIs of these approaches predicts better outcomes in research and community settings. Yet these EBIs are not widely implemented with fidelity. To help close this quality gap in adolescent services, we will develop an online intervention to strengthen fidelity to these EBIs in routine care: Fidelity Training and Feedback System (FTFS). FTFS will target two essential aspects of EBI fidelity: Training components will seek to improve EBI self-monitoring, and a Feedback component will seek to increase EBI utilization. In keeping with NIMH?s Experimental Therapeutics paradigm, this study will examine whether an Intervention (FTFS) has direct impact on its immediate Targets (EBI self-monitoring and utilization); If promising, future R01 studies will examine links among Intervention, Targets, and ultimate Outcomes (AEPs). The FTFS package will be an online quality assurance system completed by therapists and supervisors that can be readily sustained in usual care. Two weekly Training components will adapt gold-standard observational fidelity coding procedures to promote improved self-monitoring of the targeted EBIs, and a monthly Feedback component will adapt a measurement feedback system to promote increased utilization of these EBIs in everyday practice. To maximize provider investment, sites will delineate their own fidelity standards for family therapy and CBT and help design their own feedback report templates. The proposed study will be among the first to (1) test whether training therapists in observational assessment of EBI fidelity increases the accuracy with which they self-monitor use of those EBIs and (2) adapt measurement feedback procedures to track and improve therapist utilization of EBIs. To achieve study aims we will first partner with two community clinics to develop sustainable FTFS procedures using a three-phase Pilot process. We will then initiate an experimental Trial during which therapists (n = 32, treating 192 clients) at four different clinics will be randomized to FTFS versus no-intervention Control. In both conditions we will collect three kinds of data: therapist-report checklists on use of core family therapy and CBT techniques with adolescent cases, treatment session audiorecordings, and recordings of supervision meetings. FTFS uptake will be tracked electronically for online components and via observer ratings of supervision meetings (Aim 1: FTFS feasibility). Session recordings will be coded by observers for three facets of EBI fidelity: adherence (extent of EBI utilization), working alliance, and therapist competence. Observer ratings will measure the strength of EBI self-monitoring (Aim 2: therapist reliability and accuracy) and fidelity (Aim 3 [EBI utilization] & Aim 4 [alliance, competence]). If effective, FTFS could be adapted to promote EBI fidelity for a variety of clinical populations and approaches.